[Feature Request] Make DeviantArt Scrap downloader automatic

[kargaroc]

Currently, if you download a deviantart gallery, it only download the main page - the "scraps" are untouched. Now, a lot of the time, the scraps have a lot of good pictures in them.
Also, we already download folders, so it doesn't make sense that we wouldn't download scraps as part of a gallery.

I believe that, when you download a gallery, it should automatically download the scraps as well, without having to tell it to do that.

[mikf]

You can now use the deviantart.include option to tell gallery-dl what it should fetch when processing a user profile link like https://www.deviantart.com/USERNAME.